1. Field of the Invention
The present invention relates to an exposure method and an exposure apparatus to be used, for example, when a mask pattern is transferred onto a substrate in the lithography step for producing, for example, semiconductor elements, liquid crystal display elements, plasma display elements, and thin film magnetic heads. In particular, the present invention relates to an exposure apparatus in which a vibration-preventive control is adopted.
2. Description of the Related Art
A high exposure accuracy is required for the exposure apparatus of the full field exposure type (stepper type) or the scanning exposure type (for example, those based on the step-and-scan system) to be used when the semiconductor element or the like is produced. Therefore, in the exposure apparatus, an arrangement, which makes it possible to perform highly accurate positioning or highly accurate scanning, is adopted for a reticle stage on which a reticle as a mask is placed and positioned and for a wafer stage on which a wafer as a substrate is placed and two-dimensionally moved respectively.
That is, the reticle stage for the conventional exposure apparatus of the scanning exposure type is arranged, for example, such that a frame-shaped coarsely movable stage, which is movable at an approximately constant velocity in the scanning direction, is placed on a reticle base, and a finely movable stage, on which the reticle is placed, is connected into the coarsely movable stage by the aid of an actuator which is used to performing positioning in a minute amount two-dimensionally. In this arrangement, the coarsely movable stage and the finely movable stage are slidably placed on the common reticle base by the aid of air bearings respectively.
Also in the case of the reticle stage for the conventional exposure apparatus of the full field exposure type, a driving unit such as a linear motor, which is used to drive a movable stage on which the reticle is placed, is installed on the reticle stage.
On the other hand, in recent years, in order to enhance the throughput, a so-called double-wafer stage, which is provided with two movable stages, has been suggested as a wafer stage for the exposure apparatus. When the double-wafer stage is used, the throughput can be improved by performing exchange and alignment for a wafer on the second movable stage during a period in which exposure is performed for a wafer on the first movable stage. The conventional double-wafer stage has been constructed as follows in order to simplify the arrangement. That is, a guide for one axis of two orthogonal driving axes is commonly used by the two movable stages, or the two movable stages are independently driven by using plane motors.
Further, a system, which is based on the mechanical contact such that upward and downward movement is performed, for example, with a cam mechanism, is adopted for the driving system for a sample base (Z leveling stage) for performing leveling and focusing in the conventional wafer stage.
The conventional exposure apparatus has been assembled on a base plate which is installed by the aid of a plurality of (for example, four) vibration-preventive pedestals including air dampers in order to mitigate the influence of vibration from the floor. However, when an excimer laser light source is used as an exposure light source, some of members of the exposure light source and the illumination optical system are supported by support members different from the base plate. Recently, in order to allow other stage sections and other components to be not affected by the vibration generated in respective stage sections of the exposure apparatus, a system has been also suggested, in which a wafer base for supporting a wafer stage and a reticle base for supporting a reticle stage are supported mutually independently by a plurality of active type vibration-preventive units including air dampers and electromagnetic control units respectively.
Among the double-wafer stages of the conventional exposure apparatuses as described above, as for the arrangement in which the guide for one axis of the orthogonal axes is used for both of the two movable stages, an inconvenience arises such that the influence of vibration of the second movable stage tends to be transmitted to the first movable stage. For this reason, for example, it is necessary to provide certain restriction for the control sequence, for example, such that the high speed movement operation of the second movable stage is avoided during the transfer operation of the first movable stage. It has been impossible to increase the throughput so much.
Further, the conventional sample base (Z leveling stage) has been driven in accordance with the system based on the mechanical contact. Therefore, the following inconvenience arises. That is, it is impossible to increase the response speed so much, and the vibration from the bottom surface side of the movable stage tends to be transmitted to the wafer.
Taking the foregoing viewpoints into consideration, a first object of the present invention is to provide an exposure method and an exposure apparatus in which the influence of vibration is hardly transmitted among a plurality of movable stages to one another, and the exposure accuracy can be maintained to be high, when the plurality of movable stages for substrates (for example, wafers) as exposure objectives are provided.
A second object of the present invention is to provide an exposure method and an exposure apparatus in which the external vibration is hardly transmitted to a movable stage for a substrate as an exposure objective, and a high exposure accuracy can be obtained.
A third object of the present invention is to provide an exposure method and an exposure apparatus which make it possible to perform the leveling or the focusing for a substrate as an exposure objective at a high speed, in which the influence of vibration is scarcely exerted on the substrate.
Another object of the present invention is to provide a production method which makes it possible to efficiently produce the exposure apparatus as mentioned above, and a method for producing highly accurate devices, based on the use of the exposure method as mentioned above.
A first exposure method according to the present invention lies in an exposure method for exposing a second object with an exposure light beam via a first object (R1); the exposure method comprising preparing a first movable stage (14A) on which a first substrate (W1) as the second object is placed, and a second movable stage (14B) on which a second substrate (W2) as the second object is placed; two-dimensionally driving the first and second movable stages on a predetermined guide surface respectively; and dealing with reaction forces, which are generated when the first and second movable stages are driven, independently from each other.
According to the present invention as described above, the influence of vibration is scarcely transmitted mutually between the two movable stages. Therefore, the exposure accuracy is maintained to be high.
When this invention is applied to a scanning exposure type exposure method, the first object and the second object are relatively moved in a predetermined direction during the process in which a pattern on the first object is transferred to the second object. For this purpose, it is desirable that the first and second movable stages are driven while substantially satisfying law of conservation of momentum respectively when the first and second movable stages are driven in the predetermined direction. Accordingly, it is possible to perform the scanning exposure more stably.
A first exposure apparatus according to the present invention lies in an exposure apparatus for exposing a second object with an exposure light beam via a first object (R1); the exposure apparatus comprising a first movable stage (14A) on which a first substrate (W1) as the second object is placed; a second movable stage (14B) on which a second substrate (W2) as the second object is placed; and a stage-driving system (16A to 22A, 23YA, 28XA, 29XA, 16B to 22B) which drives the first movable stage and the second movable stage two-dimensionally respectively and which deals with reaction forces generated when the first and second movable stages are driven, independently from each other.
According to the present invention as described above, the two movable stages are movably placed on predetermined base members (12, 13), for example, in accordance with an air bearing system. The reaction forces, which are generated when the two movable stages are driven, are dealt with independently from each other, for example, in accordance with a system in which the law of conservation of momentum is satisfied mutually independently, or a system in which the reaction forces are released to the floor surface mutually independently. Therefore, the influence of vibration is scarcely transmitted mutually between the two movable stages. Accordingly, the exposure accuracy is maintained to be high.
The stage-driving system includes, for example, a first driving system (16A to 22A, 23YA, 28XA, 29XA) which drives the first movable stage in a first direction and a second direction which are intersected with each other respectively while substantially satisfying law of conservation of momentum; and a second driving system (16B to 22B) which drives the second movable stage in the first direction and the second direction respectively while substantially satisfying the law of conservation of momentum, independently from the first driving system. When the first and second movable stages are driven independently from each other while substantially satisfying the law of conservation of momentum as described above, the vibration of the whole of the first and second movable stages is scarcely transmitted to other stage systems and other components. Therefore, it is possible to obtain a more satisfactory exposure accuracy.
For example, the first driving system includes a pair of first slide members (19A, 20A) which are disposed in parallel to one another in the first direction (X direction) with a movement area of the first movable stage interposed therebetween and which are arranged movably in the first direction; a second slide member (16A) which is arranged movably in the second direction (Y direction) with respect to the first slide members; a first driving unit (28XA, 29XA) which relatively drives the second slide member in the first direction with respect to the first slide members; and a second driving unit (23YA) which relatively drives the first movable stage in the second direction with respect to the second slide member; and the second driving system includes a pair of third slide members (19B, 20B) which are disposed in parallel to the first slide members with a movement area of the second movable stage interposed therebetween and which are arranged movably in the first direction; a fourth slide member (16B) which is arranged movably in the second direction with respect to the third slide members; a third driving unit (28XB, 29XB) which relatively drives the fourth slide member in the first direction with respect to the third slide members; and a fourth driving unit (23YB) which relatively drives the second movable stage in the second direction with respect to the fourth slide member.
When the first slide members and the third slide members are arranged in parallel as described above, the first driving system and the second driving system can be arranged in a compact form without causing any mechanical interference.
It is desirable that the first object and the second object are relatively moved in the second direction (Y direction) when the second object is exposed with the exposure light beam; and the exposure apparatus further comprises a position-correcting driving unit which is provided to correct positions of the second slide member and the fourth slide member in the second direction respectively. This means that the present invention is applied to an exposure apparatus based on the scanning exposure system. In this case, when the scanning exposure is successively performed for respective shot areas on the first substrate or the second substrate, the position of the second slide member or the fourth slide member is corrected to be, for example, in the vicinity of the neutral position (center of the movable range) between the shots. Accordingly, the scanning exposure can be always performed while substantially satisfying the law of conservation of momentum. Thus, the exposure accuracy is improved.
In this case, when the scanning exposure is performed by successively inverting the scanning direction for a plurality of comparted areas (shot areas) arranged in one array along the first direction (non-scanning direction) on the second object, the second slide member (or the fourth slide member) performs only the reciprocating motion in accordance with the law of conservation of momentum. Therefore, the average position is scarcely changed, and it is almost unnecessary to correct the position in the second direction. On the other hand, when the exposure objective is migrated from a certain array to the next array on the second object, the second slide member remains as it is after being moved in the first direction. Therefore, it is desirable to correct the position by using the position-correcting driving unit. Accordingly, it is possible to shorten the second slide member, and it is possible to miniaturize the exposure apparatus.
It is desirable for the first exposure apparatus that the first and second movable stages are driven in first and second directions which are intersected with each other; the first object and the second object are relatively moved in the second direction when the second object is exposed with the exposure light beam; and the exposure apparatus further comprises a first position-measuring unit (35AX, 35BX) which is arranged to measure positions of the first and second movable stages in the first direction independently from each other; a plurality of second position-measuring units (36YA to 36YE) which are arranged at predetermined intervals in the first direction to measure positions of the first and second movable stages in the second direction; and a measuring unit-switching system (97) which delivers a measured value between the plurality of second position-measuring units when the first and second movable stages are moved in the first direction.
According to this arrangement, when the two movable stages are moved in the first direction in order to alternately move the two movable stages to the exposure position for the second object, the measured value of the position in the second direction is not interrupted by successively delivering the measured values obtained by the plurality of second position-measuring units. Therefore, the two movable stages can be driven highly accurately and independently from each other. Further, during the scanning exposure, the position in the second direction as the scanning direction can be continuously measured by using one second position-measuring unit (any one of 36YA to 36YE). Therefore, a high exposure accuracy is obtained.
A method for producing the first exposure apparatus according to the present invention lies in a method for producing an exposure apparatus for exposing a second object with an exposure light beam via a first object; the method comprising placing, on a predetermined base member, a first movable stage on which a first substrate as the second object is placed and a second movable stage on which a second substrate as the second object is placed; and installing a stage-driving system which drives the first and second movable stages two-dimensionally respectively and which deals with reaction forces generated when the first and second movable stages are driven, independently from each other. The first exposure apparatus of the present invention can be efficiently produced by means of the production method as described above.
In still another aspect, a second exposure method according to the present invention lies in an exposure method for exposing a second object (W1) with an exposure light beam via a first object (R1); the exposure method comprising preparing a movable stage (14A) which is arranged movably at least in a one-dimensional direction and a sample base (15A) which is arranged movably two-dimensionally with respect to the movable stage and on which the second object is placed; and two-dimensionally driving the sample base with respect to the movable stage in a plane parallel to a guide surface on which the movable stage is placed so that law of conservation of momentum is substantially satisfied.
According to the present invention, for example, the external vibration is attenuated between the movable stage and the sample base. Therefore, a high exposure accuracy is obtained.
In this arrangement, it is desirable that the sample base is supported in a state in which the sample base is tiltable and movable in a direction perpendicular to the guide surface with respect to the movable stage; and an attitude of the sample base with respect to the movable stage is controlled so that an exposure plane of the second object on the sample base is conformed to an image plane of the first object. Accordingly, it is possible to perform the leveling or the focusing for the second object at a high speed.
In still another aspect, a second exposure apparatus according to the present invention lies in an exposure apparatus for exposing a second object (W1) with an exposure light beam via a first object (R1); the exposure apparatus comprising a movable stage (14A) which is arranged movably at least in a one-dimensional direction; a sample base (15A) which is arranged movably two-dimensionally with respect to the movable stage and on which the second object is placed; and a first driving unit (42XA, 42XB, 42Y) which drives the sample base two-dimensionally with respect to the movable stage in a plane substantially parallel to a surface on which the movable stage is placed so that law of conservation of momentum is substantially satisfied.
According to the exposure apparatus as described above, the external vibration is attenuated between the movable stage and the sample base. Therefore, the vibration is hardly transmitted to the second object. Accordingly, for example, the overlay accuracy is improved, and a high exposure accuracy is obtained.
In this arrangement, it is desirable that the sample base is placed on the movable stage with a gas-based or liquid-based vibration-preventive member (40A to 40C) intervening therebetween; and the exposure apparatus further comprises a second driving unit (41ZA to 41ZC) which drives the sample base with respect to the movable stage in a non-contact state in a direction substantially perpendicular to the surface on which the movable stage is placed. The law of conservation of momentum can be satisfied with the simple arrangement owing to the vibration-preventive member, and the influence of vibration from the outside is further decreased. Further, the second driving unit makes it possible to perform the leveling or the focusing for the second object at a high speed.
In still another aspect, a third exposure apparatus according to the present invention lies in an exposure apparatus for exposing a second object (W1) with an exposure light beam via a first object (R1); the exposure apparatus comprising a movable stage (14A) which is arranged movably at least in a one-dimensional direction; a buffer member (39) which is arranged movably two-dimensionally with respect to the movable stage; a sample base (15A) which is arranged movably two-dimensionally with respect to the buffer member and on which the second object is placed; and a first driving unit (42XA, 42XB, 42Y) which drives the buffer member two-dimensionally with respect to the movable stage.
According to the exposure apparatus as described above, the external vibration is attenuated by the buffer member (39) disposed between the movable stage and the sample base. Therefore, the vibration is hardly transmitted to the second object. Accordingly, for example, the overlay accuracy is improved, and a high exposure accuracy is obtained.
In this arrangement, it is desirable that the buffer member is placed on the movable stage with a gas-based or liquid-based vibration-preventive member (40A to 40C) intervening therebetween; and the first driving unit drives the buffer member with respect to the movable stage in a plane substantially parallel to a surface on which the movable stage is placed. Accordingly, the buffer member can be driven with the simple arrangement in a state in which the law of conservation of momentum is substantially satisfied.
It is desirable that the vibration-preventive member is, for example, an electromagnetic damper having a position-measuring function.
It is desirable that the exposure apparatus further comprises a second driving unit (43XA, 43XB, 43Y) which drives the sample base two-dimensionally with respect to the buffer member in a non-contact state in the plane substantially parallel to the surface on which the movable stage is placed.
It is desirable that the exposure apparatus further comprises a third driving unit (41ZA, 41ZB, 41ZC) which drives the sample base with respect to the buffer member in a non-contact state in a direction substantially perpendicular to the surface on which the movable stage is placed at a plurality of positions. Owing to the use of the third driving unit, it is possible to perform the leveling or the focusing for the second object at a high speed.
It is desirable that the exposure apparatus further comprises a slide member (16A) which is driven in a first direction and which is arranged movably in a second direction intersecting the first direction; a fourth driving unit (23YA) which drives the movable stage relatively with respect to the slide member in the second direction; and a position-correcting driving unit (24A) which is provided to correct a position of the slide member in the second direction.
In still another aspect, a method for producing the second exposure apparatus according to the present invention lies in a method for producing an exposure apparatus for exposing a second object with an exposure light beam via a first object; the method comprising arranging a movable stage (14A) movably at least in a one-dimensional direction on a predetermined base member (12, 13); arranging, movably two-dimensionally with respect to the movable stage, a sample base (15A) on which the second object is placed; and installing a first driving unit (42XA, 42XB, 42Y) which drives the sample base two-dimensionally with respect to the movable stage in a plane substantially parallel to a surface on which the movable stage is placed so that law of conservation of momentum is substantially satisfied.
In still another aspect, a method for producing the third exposure apparatus according to the present invention lies in a method for producing an exposure apparatus for exposing a second object with an exposure light beam via a first object; the method comprising arranging a movable stage (14A) movably at least in a one-dimensional direction on a predetermined base member (12, 13); arranging a buffer member (39) movably two-dimensionally with respect to the movable stage; arranging, movably two-dimensionally with respect to the buffer member, a sample base (15A) on which the second object is placed; and installing a first driving unit (42XA, 42XB, 42Y) which drives the buffer member two-dimensionally with respect to the movable stage. According to the production methods as described above, the second and third exposure apparatuses of the present invention can be efficiently produced.
In still another aspect, a fourth exposure apparatus according to the present invention lies in an exposure apparatus for exposing a second object (W1) with an exposure light beam via a first object (R1); the exposure apparatus comprising a movable member (14A) which holds one of the first and second objects; a first guide member (16A) which defines movement of the movable member in a first direction; and a support mechanism (17A, 17B) which supports the first guide member so that the first guide member is moved while substantially satisfying-law of conservation of momentum during the movement of the movable member.
According to the exposure apparatus described above, when the movable member (for example, movable stage) is driven in the first direction, the first guide member is moved so that the law of conservation of momentum is satisfied. Therefore, the influence of vibration is mitigated.
In this arrangement, it is desirable that the movable member is coupled to the first guide member substantially in a non-contact manner, and the support mechanism supports the first guide member substantially in a non-contact manner. Accordingly, the influence of external vibration is further reduced.
It is desirable that the exposure apparatus further comprises a driving unit (28XA, 29XA) which drives the first guide member so that the movable member is moved in a second direction perpendicular to the first direction, and a second guide member (19A, 20A) which defines movement of the first guide member in the second direction, wherein the second guide member is moved while satisfying the law of conservation of momentum during the movement of the movable member.
Accordingly, the movable member (movable stage) is driven so that the law of conservation of momentum is satisfied in the two directions perpendicular to one another. Therefore, the influence of vibration is reduced even when the movable member is driven in any direction.
In still another aspect, a fifth exposure apparatus according to the present invention lies in an exposure apparatus for exposing a second object (W1) with an exposure light beam via a first object (R1); the exposure apparatus comprising a movable member (W1) which holds one of the first and second objects; a first guide member (16A) which defines movement of the movable member in a first direction and which is movable in a second direction perpendicular to the first direction; a second guide member (19A, 20A) which defines movement of the first guide member in the second direction; and a support mechanism (21A, 22A) which supports the second guide member so that the second guide member is moved while substantially satisfying law of conservation of momentum during the movement of the movable member.
According to the exposure apparatus as described above, when the movable member (movable stage) is driven in the second direction by the aid of the second guide member, the second guide member is moved so that the law of conservation of momentum is satisfied. Therefore, the influence of vibration is reduced.
In the arrangements described above, for example, the first and second objects are relatively moved with respect to the exposure light beam respectively to perform scanning exposure for the second object with the exposure light beam; and the movable member holds the second object, and the movable member is moved in the first direction during the scanning exposure.
In still another aspect, a method for producing a device according to the present invention comprises the step of performing exposure by using any one of the exposure methods and the exposure apparatuses of the present invention. The influence of vibration is mitigated, and a high exposure accuracy is obtained according to the present invention. Therefore, it is possible to produce the device having the high function which is excellent, for example, in pattern faithfulness (for example, line width resolution).